It gives you righteous mandate for additional tank heals and a heal for the target with this buff. You also gain the instant cast heal from sentinel and a casted heal if need be but the points here are more for the sp and crit bonus to dmg/heals.

This is typically the spec I run when we need extra raid heals. Note I did not take 10% mana reduction because with the changes to agressive renewal mana simply is not an issue anymore and it allows you to put more points into justicar.

It lets you stay at ranged and is a good all-situations packaged build. While the healing output may not be as large as a warden/sent specc it does have alot of clutch healing tools for both single target and AE... while still offering DPS. The Sentinels passives: Spell Power +5% and +20% to Crit Hit and Healing bonus make it a nice compliment to the Inquisitor tree.

Healing:AE healing (Technically you get 3)1 Small vias: Healing Breath (hits 3 players)1 Medium: Healing Communion - 10 players 2 sec cast time Spamming this with serendipity proc'd will give you .5 sec AE healing that puts out a large amount over a short period of time.1 Large Instant cast: Divine Call - 1 min CD

For this build with regards to healing, Serendipity is the key - it lasts 60 secs, procs often and affects both your long cast time AE and Single target heals. If that isnt enough for those clutch healing moments you also get Touch the Light (45s CD) which makes your next Heal instant cast.

-Banish has a horrible co-efficent. I would not recommend ever using this as the gcd casting something else would do more dmg
-Life's Vengeance is ok but without it being buffed by warden's 10% to instant spells it is very far behind also.
-I would also stray away from shard's of light. Reason is the dmg on it did get nerfed at one point. It was viable for an inquis build but now it doesn't add much and is rather clunky channel for an already decent rotation.

My only real problems with this spec is that you cannot get enough points into Inquis to get the 36 point passive that boosts your dot dmg. So while the spec gives you decent utility you are sacraficing alot in the dps and healing area so not really doing either well. The Inquis/Justicar spec is more of a chloro like raid healing build that also allows you to give a tank extra heals that only sacrafices 150-200dps max vs a pure inquis spec.

Couple inquis talents i'd stray away from for a raid DPS/Heal build as well are Lethargy, Bewilder, harsh discipline, Contempt. The reasons for this are all your dmg already heals you so no need to waste points. I've yet to find bewilder useful anywhere as it doesn't seem to do a whole lot and the snare from lethargy not really useful in todays pve environment.

Of course this is just my opinion just thought i'd give my viewpoint from a DPS standpoint having used a DPS/Healing support tree fairly often.